This DIY Project introduces the force of gravity. Since ancient times, there have been numerous theories and attempts to explain this mysterious force called “gravity”. During the early days, philosophers thought that the falling of objects toward the Earth was part of the gods’ realm and followed a natural motion. For instance, air belonged in the heavens, moving upward, while rocks belonged to the Earth, falling back to Earth.

“Take a moment to experience the effects of gravity. Lift your arm and feel how you are compelled to drop it again.”

In the 17th century, an Italian astronomer, Galileo Galilei, provided gravity’s first scientific explanation by conducting experiments and challenged the idea of gravity proposed by Aristotle.

Through his experiments, Galileo realized that a falling body picked up speed at a constant rate—in other words, it had constant acceleration. He also made the significant observation that, if air resistance can be neglected, all bodies fall with the same acceleration, bodies of different weights dropped together reach the ground simultaneously.

Galileo is said to have dropped balls of the same shape but different weight from the leaning Tower of Pisa to demonstrate that the objects fell with the same acceleration.

When air resistance is present, an object’s shape can make things tricky because large, flat, light objects (like a flat sheet of paper) are slowed down more by air resistance than are smaller, smoother objects.

In this activity, the students will use a book and a paper to learn gravitational force pulls objects towards the Earth at the same rate, regardless of mass.

Difficulty: Easy

Average Time: 3-5 Minutes

MATERIALS

• A Book, that you can drop on the floor.
• A Bond paper, the same size as the book.

DISCUSSION

In the first demo (Steps 1 and 2), the book falls faster through the air than the paper when they are dropped side by side. Although gravitational pull on both paper and the book is the same, the paper’s air resistance is much larger than the book as the paper is much lighter. However, the book had more mass, so that it had more force to push through the air resistance.

In the second demo (Steps 3 and 4), the paper is placed on top of the book. The air can’t reach the bottom of the paper as the book shields it. This made both the paper and the book fall at the same rate as the paper’s air resistance was almost negligible.

In the final demo(steps 5 and 6), we changed the shape of the paper to demonstrate how the shape of an object can affect air resistance. By wrinkling up the paper, the surface area of the paper is reduced.